Guidelines. Every spacing rule and typical size on this site comes from a published guide by a furniture maker, retailer, the Sleep Foundation or OSHA, named and linked on the page. Different guides sometimes give slightly different numbers; when they do, we show both.
Calculators. Our calculators apply those published rules with plain arithmetic. They are a starting point: measure your own space and check the maker's dimensions before you buy.
Shopping links. Some links go to store search results, and we may earn a commission. That never changes the numbers.
Checked October 17, 2026.